Matt,
I don't like the added weight behind the rear axle, especially on short wheelbase vehicles. The spare tire is usually fairly far from the back of the jeep, more so with fuel cans mounted. A swing out rear bumper is generally about 100lbs, spare tire is 50-100lbs, fuel cans are about 50lbs each. That stuff adds up WAY fast. All the weight is also behind the rear axle, so it not only adds weight to the rear axle, it also takes weight OFF the front axle in leverage. This really starts to mess with vehicle dynamics on a SWB while trying to climb things.
Again, just my own opinion.....